Remove Node v6 from test matrix and clarify support in README

Author: kadamwhite

.travis.yml

@@ -5,6 +5,5 @@ node_js:
   - "lts/*"
   - "10"
   - "8"
-  - "6"
 # Opt-in to travis container infrastructure
 sudo: false

README.md

@@ -41,7 +41,9 @@ To get started, `npm install wpapi` or [download the browser build](https://wp-a
 
 ## Installation
 
-`node-wpapi` works both on the server or in the browser. Node.js version 4.0 or higher is required.
+`node-wpapi` works both on the server or in the browser. Node.js version 8 or higher is required, and the latest LTS release is recommended.
+
+In the browser `node-wpapi` officially supports the latest two versions of all evergreen browsers, and Internet Explorer 11.
 
 ### Install with NPM